Energy utilization and activity patterns of the vole arvicola terrestris amphibius (l)

Abstract

The energy assimilated by a small population of Arvicola terrestris amphibius (L.) occupying a 380m stretch of stream in south Durham was calculated by quantifying the parameters of population respiration and tissue production and was subsequently related to the available food supply. The changes in population density, size and age structure were monitored by frequent live-trapping over the entire calendar year and an assessment was made of the population structure and tissue production over consecutive periods of twenty days. The temperature - and above-ground activity experience of representatives of the population were investigated implementing artificial burrow systems built into outdoor enclosures under simulated stream conditions. The pattern of day to day activity was monitored by recording thermo graphs which registered the temperature changes in vole nests caused by the intermittent presence of the animal's body heat. Nest chamber and soil surface temperatures were recorded concurrently. The patterns of vole activity were analysed and related to conditions of social inter-reaction and to variations in weather parameters. The oxygen consumption of representative members of the population was investigated at a range of experimental temperature during periods of both rest and activity by means of a closed-circuit respirometer. The population respiration demand was estimated over consecutive periods of 20 days with corrections included for the seasonal variation in population size and age structure, ambient temperature and the proportion and quality of above-ground activity. The available food supply was estimated by regular sampling of the vegetation within the feeding range in conjunction with an investigation of the rate of plant decomposition. The feeding preferences of the population were examined and the energy flow between primary and secondary production deduced.